Spot the Hockey Stick! #4 – The US Climate Change Program

Another sighting of our favorite climate reconstruction is to be found at the "Strategic Plan for the Climate Change, Science Program, Final Report, July 2003", published by the US Climate Change Science Program.

Climate research has indicated that, globally, it is very likely that the 1990s were the warmest decade in the instrumental record, which extends back to the 1860s (see Figure 4-1); large climate changes can occur within decades or less, yet last for centuries or longer; and the increase in Northern Hemisphere surface temperatures during the 20th century likely exceeds the natural variability of the past 1,000 years (IPCC, 2001a, d).

Placing instrumental records in the context of longer-term variability through paleoclimate analyses has played a key role in these findings. Moreover, observational evidence together with model simulations incorporating a comprehensive suite of natural and anthropogenic forcings indicate that "…the changes observed over the last several decades are likely mostly due to human activities, but we cannot rule out that some significant part of these changes is also a reflection of natural variability" (see Figure 4-2) (NRC, 2001a).

All climate models used in the most recent Intergovernmental Panel on Climate Change (IPCC) assessment project that global mean temperatures will continue to increase in the 21st century and will be accompanied by other important environmental changes, such as sea level rise, although the magnitudes of the projected changes vary significantly depending on the specific models and emissions scenarios (IPCC, 2001a, d).

Figure 4-1: Top Panel: Changes in the Earth’s surface temperature over the period of direct temperature measurements (1860 — 2000). The global mean surface temperature is shown each year by the red bars (with very likely ranges as thin black lines) and approximately decade-by-decade by the continuous red line. Bottom Panel: Proxy data (year-by-year blue line with very likely ranges as gray band, 50-year-average purple line) merged with the direct temperature measurements (red line) for the Northern Hemisphere. The proxy data consist of tree rings, corals, ice cores, and historical records that have been calibrated against thermometer data. Source: IPCC (2001d).

I don’t like the way this graph is drawn. blue for cold, red for hot (instrumental recent versus proxy). The instrumental info added on in such a way that it obscures the less upticking proxy. The horizontal line like a threshold barriar that has been peirced.